Aerobic exercise impacts bodily processes implicated in the pathophysiology of major depression. Consistent with these effects, aerobic exercise in general, and running in particular, has been repeatedly shown to have both immediate mood elevating and longer-term antidepressant effects. To the investigators' knowledge, all studies of running as a therapeutic intervention for mood have had subjects run in standard running shoes, despite increasing evidence that running barefoot or in shoes with minimal effect on foot strike (i.e. "minimally shod") leads to marked changes in how people run in ways that might have physiological effects of relevance to health. Thus, nothing is currently known about differences in effects on depression-relevant physiological or emotional functioning between running either barefoot or minimally-shod vs. running in standard running shoes (hereafter called "shoed). The current pilot study is designed to begin addressing these issues by examining effects of minimally shod vs. shoed running on non-invasive measures of autonomic nervous system (ANS) functioning and mood state.